Page:Popular Science Monthly Volume 12.djvu/577

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THE TELEPHONE AND HOW IT WORKS.

taken even in weak doses it causes restlessness and anxiety, a sort of feverish activity altogether different from the indolent activity of opium. Under the action of opium the will seems to be lulled to sleep and the imagination runs riot. But under the influence of coffee the imagination is hardly stimulated at all, while there does appear to be excitation of the will. Did I not fear being suspected of having a theory to defend, I should say that the faculties of will and consciousness seem to be superexcited: there is, as it were, a constant strain on attention and memory, whereas in the case of alcohol, hasheesh, and opium, there is a relaxing of attention. Hence coffee produces a true intoxication that fatigues one far more than does the somnolent intoxication of opium, but it leads to the same result. In striving to do too much, the mind does less: under stimulation the will is impaired; and the perfect equilibrium of the mental faculties is disturbed as well by excess as by defect of will.

Coffee is said to produce cerebral anæmia, while opium and alcohol cause congestion; but this theory still needs confirmation. Nevertheless, the part played by coffee in general nutrition is very well understood. It retards organic combustion, and hence it is an aliment d'epargne—a food-stuff that effects a saving of other food-stuffs. In the normal state there is always going on within our tissues a multitude of chemical actions, the final result of which is heat-production and liberation of carbonic acid. This carbonic acid passes into the venous blood, and the venous blood, on reaching the lungs, parts with its carbonic acid. Thus the quantity of the carbonic acid is, to some extent, the expression of the nutritive activity. Now, on taking coffee, though no greater quantity of oxygen be inhaled, and without increasing the ration of food, the quantity of the carbonic acid is reduced, and yet the amount of force is not lessened. As illustrating this doctrine, it is usual to cite a fact observed among Belgian miners, who can perform a considerable amount of work almost without food, their strength being maintained solely by the absorption of a large quantity of coffee. Hence coffee is a food-stuff which moderates nutrition by lessening the activity of the chemical transformations incessantly going on within the tissues.

 
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THE TELEPHONE AND HOW IT WORKS.
By GEORGE M. SHAW.

AMONG the innumerable uses of electricity none is more remarkable than its employment for the transmission of sound. The ultimate mystery of the action we cannot, of course, undertake to explain, but the mechanism by which it is produced is by no means difficult to understand.